import java.util.Scanner;

public class Main{
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        int sum = 1;
        if(n == 0){
            sum = 1;
        }
        else if(n > 0){
            for (int i = 1; i <= n; i++) {
                sum = sum * i;
            }
        }
        System.out.println(sum);
    }
}